Bicycles have evolved over many decades into highly efficient machines. They are strong, stiff, and amazingly light in weight. They are not, however, aerodynamically efficient.
Athletes have turned towards aerodynamics with the hope that a more aerodynamic bicycle or position will make them go faster and reduce time in a race. New wheel designs have attempted to reduce the drag created by the rotating wheels. The common spoked wheels, when rotating at any speed, act as turbines and provide a great amount of drag. Several designers have reduced the number of spokes and/or installed the spokes radially. This has somewhat reduced the turbine air-pumping effect. Others have turned towards disc wheels, aero rims, or composite aero wheels. These changes, however, only reduce the drag created by the wheels and do not contribute towards reducing the drag created by the rider, one of the major sources of drag.
Some designers have attempted to decrease the drag created by the rider by providing aero handlebars, or "aero bars." Aero bars became popular after Greg LeMond won the Tour de France in 1989 and 1990 while using them. Aero bars stretch out the rider by forcing the rider to ride with his or her back almost horizontal and arms extended forward. This reduces the frontal area and helps the rider "slice" through the air. Additionally, because the aero bars stretch out the rider and the rider's back is flattened, drag due to the suction created behind the rider is reduced, again because of the lower effective area presented to the suction.
One drawback of the modern aero position is poor leverage and control for climbing or sprinting, particularly if the rider rides out of the saddle. Furthermore, because the braking controls are not integrated within the aero bars, they are not immediately accessible to the rider and are also out in the airstream and add drag. The usual arrangement of a bicycle equipped with standard handle bars and clip on aero bars is, accordingly, not ideal.